Conventionally, a gas-blast circuit breaker has a function to extinguish an arc by spraying arc extinguishing gas such as SF6 gas to the arc generated between electrodes when an electric circuit is cut off. Since insulation performance of the arc extinguishing gas is generally reduced at a high temperature, heat removal is necessary after the arc extinguish gas is heated in spraying to the arc.
Thus, the gas-blast circuit breaker of this type has a cooling cylinder, for example, constituting a flow path for heat removal of the arc extinguishing gas on a downstream side between the above-described electrodes. Here, in a situation that heat removal performance by the cooling cylinder is insufficient, resulting in reduction of the insulation performance of the arc extinguishing gas, there is a possibility that dielectric breakdown occurs between a tank of ground potential which is a casing of the gas-blast circuit breaker and the cooling cylinder of high voltage which is housed in this tank. In consideration of the problem of dielectric breakdown as above, a comparatively large space is secured in the gas-blast circuit breaker in order to give a certain or more interval between the tank and the cooling cylinder.
On the other hand, in order to reduce a disposition space for disposing a main body of the gas-blast circuit breaker or to curtail material costs of components of the gas-blast circuit breaker, downsizing of the gas-blast circuit breaker is demanded. In downsizing the gas-blast circuit breaker, considering the above-described problem of dielectric breakdown, it is important to improve the heat removal performance to the arc extinguishing gas. Further, regarding a configuration for improving the heat removal performance, it is required to consider a pressure loss of the arc extinguishing gas flowing in the flow path such as the cooling cylinder.